Centrifuge

ABSTRACT

A centrifuge designed primarily but not exclusively for paving mix analysis procedures includes a rotatable bowl and having an upper steady bearing assembly secured to the centrifuge body cover. Inlets are provided through the bearing assembly for either solvent alone or for dissolved bitumen aggregate and suspended particulate matter. The bowl has an annular U-shaped trap around the periphery thereof adjacent the junction of the centrifuge bowl and a cover therefor with a filter therebetween, which traps clay sized particulate matter which might migrate between the filter paper and the centrifuge bowl surface thus giving a more complete retention of particulate matter and thereby allow a more accurate analysis than heretofore.

States Patent 1191 Pronk 1451 Feb. 4, 1975 CENTRIFUGE [75] Inventor: Frank E. Pronk, Calgary, Alberta,

Canada [73] Assignee: R. M. Hardy Associates Ltd.,

Calgary, Alberta, Canada [22] Filed: Aug. 8, 1973 [21] Appl. No.: 386,770

[52] US. Cl 233/2, 233/21, 233/27, 233/47 R [51] Int. Cl. B04b [58] Field of Search 233/1 R, 1 D, 1 A, 2, 27, 233/28, 21, 46, 47 R [5 6] References Cited UNITED STATES PATENTS l,074,4l0 9/l9l3 Crocker 233/27 X 2,435,665 2/l948 Woolaver 233/2 X 2,448,038 8/1948 Lykken et al 233/27 X 2,785,765 3/l957 Cornell 233/28 X 3,023,949 3/1962 Bankerd 233/47 R 3,443,748 5/1969 Hooper 233/28 FOREIGN PATENTS OR APPLICATIONS 253,653 6/1926 Great Britain 233/2 7/l954 Belgium ..233/2 4/1961 Germany ..233/2 Primary Examiner-George H. Krizmanich Attorney, Agent, or Firm-Stanley G. Ade

[57] ABSTRACT A centrifuge designed primarily but not exclusively for paving mix analysis procedures includes a rotatable bowl and having an upper steady bearing assembly secured to the centrifuge body cover. lnlets are provided through the bearing assembly for either solvent alone or for dissolved bitumen aggregate and suspended particulate matter. The bowl has an annular U-shaped trap around the periphery thereof adjacent the junction of the centrifuge bowl and a cover therefor with a filter therebetween, which traps clay sized particulate matter which might migrate between the filter paper and the centrifuge bowl surface thus giving a more complete retention of particulate matter and thereby allow a more accurate analysis than heretofore.

4 Claims, 4 Drawing Figures Pmmm w 191s SHEET 10F 2 FIG.

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PATENTEDFEB 41915 3.863.838

SHEET 2 [IF 2 120v, so CYCLE AC cuanem' |7 l P l TIMER cou'raoL FOR '6 H H |2 nPuuP mm M 1' M 83 2: 288.2828 mums AUTOMATIO on 231%.? ii i 5 among ou oguvznv i "I f SPEED oomnol. mo

i} 'rAcaounza ron .1 V OENTRIIUGI MOTOR SOLVENT FROM 45 GAL.

SUPPLY BARREL GRAVI FLOW OF DIRTY SOLVENT AND HIM-I3 ZOO SCREEN SIZE AGGREGATE FRACTION IN SUSPENGION DIRTY SOLVENT MAY BE REOOVERED mo DISTILLED $225 FOR RE-USC =NO'IOR CENTRIFUGE BACKGROUND OF THE INVENTION The centrifuge of the present application is designed primarily for use with equipment for the separation of unsoluble granular materials from solutions or soluble binders from aggregate-binder systems such as paving mix analysis and the like.

Conventionally, the systems in present use require recovery of portions or all of the centrifuge effluent. A secondary, lengthy process must be carried out in order to determine the quantity of suspended solids contained therein.

This is time consuming and therefore extremely inefficient for quality control purposes.

SUMMARY OF THE INVENTION The present invention provides means whereby completely automatic separation of bitumen from aggregates can be accomplished and if used with a wet sieve unit, provides the separation of the aggregates into various sieve fractions. The use of the centrifuge hereinafter to be described permits the recovery of the minus No. 200 screen size aggregate from the solution in one operation thereby eliminating the necessity for the time consuming recovery processes of this particular fraction.

Furthermore, the centrifuge permits extractions to be carried out in the centrifuge only thus by-passing the shaker unit or wet sieve unit, once again enabling essentially all of the sediments to be recovered.

The principal object and essence of the invention is therefore to provide a centrifuge of the character herewithin described which is adapted to efficiently separate suspended solids from solution, thereby eliminating the separate process normally required for the recovery of suspended solids from the centrifuge effluent.

Another object of the invention is to provide a device of the character herewithin described which incorporates a novel upper steady bearing assembly for the drive shaft at the centrifuge.

Still another object of the invention is to provide a device of the character herewithin described which has connections enabling the solution containing suspended solids to be conveyed to the centrifuge on a continuous basis from a wet sieve unit or the like together with a further connection which enables solvent only to be conveyed to the centrifuge bowl which under these circumstances, may contain the sample of paving mix being tested thus by-passing the shaker unit or wet sieve unit.

Another object of the invention is to provide a device of the character herewithin described which includes an annular sediment trap around the perimeter of the bowl and adjacent the cover and filter medium which traps extremely fine particles which might migrate between the filter medium and the upper edge of the bowl during use, thus giving a more complete retention of particulate matter and thereby allow an accurate analysis without the aid of a secondary, lengthy recovery process. Still another object of the invention is to provide a device which in conjunction with a suitable wet sieving unit, provides for the automatic separation of bitumen from a paving mix and the automatic separation of the recovered aggregates according to particle size, including the minus No. 200 screen size fraction thus enabling an analysis to be made of the paving mix sample in approximately 1 hour and 15 minutes total elapsed time from the start of the test.

A still further object of the invention is to provide a device of the character herewithin described which can be used in other environments than that described herein.

A still further object of the invention is to provide a device of the character herewithin described which is simple in construction, economical in manufacture and otherwise well suited to the purpose for which it is designed.

With the foregoing objects in view. and other such objects and advantages as will become apparent to those skilled in the art to which this invention relates as this specification proceeds, my invention consists essentially in the arrangement and construction of parts all as hereinafter more particularly described, reference being had to the accompanying drawings in which:-

DESCRIPTION OF THE DRAWINGS FIG. 1 is a cross sectional view of the centrifuge per FIG. 2 is a top plan view of FIG. 1.

FIG. 3 is a schematic view showing the device used with a wet sieving extractor.

FIG. 4 is a cross section of the centrifuge bowl per se.

In the drawings like characters of reference indicate corresponding parts in the different figures.

DETAILED DESCRIPTION Although there are known wet sieving extractors and filler recovery equipment for bituminous mix analysis, there is no known commercial system that will reliably perform bitumen extraction, aggregate gradation and filler (minus No. 200 screen size aggregate) separation in one automatic operation.

Conventionally, centrifuges used for the separation of bitumen from aggregate in bituminous mixes, em-

ploy systems whereby the solvent is manually batched into the centrifuge bowl at certain intervals during the extraction cycle and it is not believed that any practical system exists which may employ a combination of wet sieving and filler separation by centrifuge in an automatic cycle.

Dealing first with FIG. 3, the centrifuge collectively designated 10 is shown in conjunction with a wet sieve extractor collectively designated 11 although it will of course be appreciated that a batch of paving mix may be placed directly within the centrifuge and separated as will hereinafter be described.

In the system shown in FIG. 3, a plurality of screens 12 are held in spaced and parallel relationship within the main body 13, and said screens decreasing in mesh size from the upper end towards the lower end, with the lowermost screen 14 having a No. 200 mesh, for example.

The batch to be analyzed is placed on the uppermost screen and the shaker unit is operated from the motor 15 and a controlled volume pump 16 feeds solvent from a bulk supply (not illustrated) into the upper end of the sieving extractor as indicated by arrowed line 17.

This dissolves all the bitumen in the sample and the shaker unit separates the various grades of aggregate according to the sizes of the sieves within the stack.

As an example, the sieve stack may consist of the following screen sizes: of an inch, No. 4, No. 8, No. 16, No. 30, No. 50, No. I and No. 200.

While the soluble binder and fines which pass through the No. 200 screen, leave the extractor, the aggregate is automatically sorted into various sizes controlled by the above mentioned set of screens so that, once it has been dried, accurate weight analysis of the various sized aggregates is easily determined.

The solvent leaving the extractor, together with the dissolved bitumen and the minus No. 200 screen size aggregate fraction, flow by gravity along the part indicated gy arrowed line 18, to the centrifuge 10. Details of this centrifuge construction are shown in FIGS. 1 and 2.

The centrifuge consists of a substantially cylindrical body portion collectively designated 19 which includes a vertical annular portion 20, an inwardly sloping portion 21 and a supporting base portion 22 secured thereto by means of cap screws 23.

The base also includes a vertically situated drive shaft 24 having a reduced shoulder portion 25 extending upwardly from the upper end thereof.

The centrifuge housing cover 26 is disc shaped and is provided with an annular groove 27 around the underside thereof adjacent the periphery engageable with or upon a housing cover ring 28 having a cross section as illustrated and acting as a seal between the housing 19 and the cover 26 as well as acting as a location means for the cover relative to the housing. The cover 26 is detachably clamped to the housing by means of a plurality of hinged clamps 29 tightened by means of wing nuts 30. The annular seal ring 28 is secured in turn to the upper edge of the housing by means of recessed screws 31.

The aforementioned vertically situated drive shaft 24 is connected to a source of power indicated schematically by reference character 32 in FIG. 3 and the drive shaft is supported adjacent the lower end thereof within a bearing shown schematically in FIG. 1 and identified by reference character 33.

The centrifuge bowl collectively designated 34 is provided with a hollow central hub 35 shaped to engage over the drive shaft 24 which extends upwardly through the housing 19 and terminates in a tapered upper end 36. In this connection, apair of projections 37 extend outwardly from the drive shaft adjacent the central base plate 38 of the housing and corresponding slots 39 are provided at the base of the hub 35 which engage over these projections thus transmitting the rotational drive of the shaft to the bowl 34.

When used in an environment for which this centrifuge is designed, it is necessary to provide bearing support at the upper end of shaft 24 to prevent any sideways strain or radial strain being placed upon the bowl when being rotated and in this connection, a steady bearing assembly collectively designated 40 is provided centrally of the housing cover 26. It consists of a cylin drical bearing housing 4] secured centrally of the cover 26 and upon the underside thereof by means of a plurality of cap screws 42 or the like, a bearing 43 engages over the tapered upper end 36 of the shaft and seats within an annular recess 44 in the bearing housing 40 thus steadying the shaft 24 and supplying bearing support aa the upper end thereof.

Extending through this assembly is a tube or conduit 49 surrounded by a gland nut 46 and this conduit screw threadably engages the upper end of a drilling 47 extending through the bearing housing 4l thus communicating with the interior of the bowl through a central aperture 47 formed centrally within the bowl cover collectively designated 48 and which will hereinafter be described.

This conduit 49 is connected to a source of solvent which is fed to the interior of the bowl under pressure and is used when a batch of paving mix is placed directly in the bowl for separation of the aggregate from the soluble fractions. In this regard a nozzle 49A is secured to the inner end of the conduit and facilitates efficient spraying of the solvent onto the paving mix.

If however, the centrifuge is used with the wet sieve extractor shown schematically in FIG. 3, then the solvent from the base of the extractor, together with the dissolved portions and the minus No. 200 screen size aggregate fraction, is connected to a further conduit also extending through the bearing housing 4l and being secured in a manner similar to conduit 49. Once again this conduit communicates with the interior of the bowl 34 through the central aperture 47 within the cover thereof.

A detachable cap, screw 50 is provided within the center of the housing cover 26 which may be removed for inspection purposes or checking of drive shaft speed by direct reading of mechanical tachometer (not illustrated).

The aforementioned bowl 34 includes the hub 35 and the bowl-shaped outer wall 51 extending from the hub upwardly and outwardly, terminating in a horizontally situated annular flange 52 which acts as a seating for the cover 48.

The cover 48 is disc shaped and is provided with an upwardly extending annular collar 53 bounding the central aperture 47.

A plurality of overflow or return drain channels or drillings 54 are provided within the portion of the cover 48 bounding the central aperture 47, said drillings extending outwardly and downwardly around the aperture 47 as clearly shown.

These are provided because as solvent or the like is continually being fed to the rotating bowl 34, some splash may occur which may cause the solvent together with any fines suspended therein to splash upwardly between the housing and the flange 53. This is then returned via the drillings 54 so that no fines are lost during the separating operation.

A disc of filtering medium such as filter paper 55 is centrally apertured to pass over the hub 35 at the upper end thereof and engages upon the horizontally situated annular flange 52 and the cover is then clamped to this flange by means of a plurality of bolts and wing nuts 56 so that during operation, the solvent is centrifugally moved through the filter medium between the cover 48 and the flange 52.

Under certain circumstances, some of the extremely fine clay-like material may migrate between the filter paper 55 and the flange 52 which would tend to give a false reading to the result. This is prevented by the provision of an annularly situated sediment trap collectively designated 57 and formed on the outer edge of the flange 52. This U-shaped trap is vertically situated and extends above the plane of the flange 52 which is indicated by the dotted line 58. This provides an annular U-shaped channel immediately outboard of the periphery 59 of the bowl cover 48 and traps fine sediment therein. 7

As mentioned previously, two modes of operation for this centrifuge for bituminous paving mix analysis are provided.

Firstly, the centrifuge may be used with the wet sieving extractor as indicated by reference character 11 in FIG. 3. Under these circumstances, a bituminous mix sample is placed on the top screen and the top of the unit is closed to isolate and secure the sieve stack. During the analysis cycle, a constant volume of solvent is sprayed onto the top screen which in conjunction with the vertical shaking action of the shaker unit, results in a complete rapid extraction of the bitumen as well as the separation and collection of aggregate sizes on the stack of sieves. All aggregate passing the bottom screen is then transported into the centrifuge as suspended matter within the solution and enters the centrifuge through conduit 45. These aggregate particles are then retained in the centrifuge with the dissolved bitumen passing through the filter paper or filtering medium 55, it being noted that any extremely fine particles which may migrate between the flange 52 and the filter paper 55 are trapped in the sediment trap 57.

lmmediately following this cycle, the sieve stack and centrifuge bowl with the filter paper is removed and placed in a warm oven or the like for drying. Following this the dry aggregate fractions retained on each sieve as well as the dry aggregate retained in the centrifuge are weighed and the sieveanalysis for the aggregate plus bitumen content for the paving mix are calculated, the bitumen content being the weight difference between the sample prior to the paving mix analysis cycle and the total dry aggregate weight after the cycle.

In the second mode, where the centrifuge is used without the wet sieve extractor 11, the bituminous mix sample is placed directly into the centrifuge bowl. The solvent is then automatically introduced into the bowl via conduit 49, with'the cycle continuing until all bitumen has been removed from the centrifuge bowl.

Following the completionof this cycle, a regular sieve analysis of the aggregate is still required if aggregate grading is required.

The important points of construction of the centrifuge are the unique design of the bearing block assembly 40 together with the unique design of the bowl cover 48, the bow] itself and the provision of the sediment trap 57.

The device provides a rapid method for recovery of suspended particle matter from low concentration suspensions with essentially no loss of particulate matter.

Finally, although the principal intended use of this equipment is (a) for the rapid separation of mineral filler from bitumen solution or (b) bitumen from aggregate-binder systems, it may be utilized for any application where a rapid, continuous and efficient high capacity separation of insoluble particles from a solution is desired.

Since various modifications can be made in my invention as hereinabove described, and many appar' ently widely different embodiments of same made within the spirit and scope of the claims without departing from such spirit and scope, it is intended that all matter contained in the accompanying specification shall be interpreted as illustrative only and not in a limiting sense.

What i claim as my invention is:

l. A centrifuge assembly comprising in combination a vertically situated body portion, a drive shaft extending upwardly into said body portion from the base thereof, means to support said drive shaft for rotation within the said base of said body portion, a centrifuge bowl having an upper side bounded by a peripherial rim, detachably engaged for rotation over said drive shaft and within said body portion, a centrally'apertureddetachable cover 'for said bowl in clamping engagement with said rim, a filtering medium operativ'ely clamped between said detachable cover and said rim of said bowl, a detachable cover for said body portion, an upper drive shaft steady bearing assembly secured to said cover for said body portion, bearably engaging over the upper end of said drive shaft, and an annular vertically situated U-shaped sediment trap formed around the periphery ofsaid bowl and extending substantially above the horizontal plane of said rim of said bowl.

I 2. The assembly according to claim 1 which includes tending downwardly and outwardly from the portion of the cover of said bowl bounding said central aperture and returning splashed material by centrifugal force when said bowl is rotating.

3. The assembly according to claim 1 in which said steady bearing assembly includes a cylindrical portion detachably secured to the underside of said cover for said body portion, and a bearing assembly receivable withinsaid cylindrical portion and engaging over said drive shaft.

4. The assembly according to claim 2 in which said steady bearingassembly includes a cylindrical portion detachably, secured to the underside of said cover for said body portion, and a bearing assembly receivable within said cylindrical portion and engaging over said drive shaft. 

1. A centrifuge assembly comprising in combination a vertically situated body portion, a drive shaft extending upwardly into said body portion from the base thereof, means to support said drive shaft for rotation within the said base of said body portion, a centrifuge bowl having an upper side bounded by a peripherial rim, detachably engaged for rotation over said drive shaft and within said body portion, a centrally apertured detachable cover for said bowl in clamping engagement with said rim, a filtering medium operatively clamped between said detachable cover and said rim of said bowl, a detachable cover for said body portion, an upper drive shaft steady bearing assembly secured to said cover for said body portion, bearably engaging over the upper end of said drive shaft, and an annular vertically situated U-shaped sediment trap formed around the periphery of said bowl and extending substantially above the horizontal plane of said rim of said bowl.
 2. The assembly according to claim 1 which includes a plurality of overflow return channels through said cover of said bowl adjacent the center thereof for returning to said bowl, material splashed upwardly from said bowl between said steady bearing and the central aperture in the cover of said bowl, said channels extending downwardly and outwardly from the portion of the cover of said bowl bounding said central aperture and returning splashed material by centrifugal force when said bowl is rotating.
 3. The assembly according to claim 1 in which said steady bearing assembly includes a cylindrical portion detachably secured to the underside of said cover for said body portion, and a bearing assembly receivable within said cylindrical portion and engaging over said drive shaft.
 4. The assembly according to claim 2 in which said steady bearing assembly includes a cylindrical portion detachably secured to the underside of said cover for said body portion, and a bearing assembly receivable within said cylindrical portion and engaging over said drive shaft. 